NF Electrode Research Articles

Three-dimensional carbon interdigitated ring array nanofibers for electrochemical detection of dopamine neurotransmitter

Dopamine (DA) neurotransmitter is a prominent component of the central nervous system and its deficiency contributes to several diseases, such as Parkinson’s disease and schizophrenia, which significantly influence the quality of life of affected individuals. This paper introduces a circular interdigitated ring electrode, the three-dimensional carbon interdigitated ring array nanofibers (3D C-IDRA NFs), for the detection of DA using amperometric detection. The study utilized cyclic voltammetry and chronoamperometry to investigate DA. The integration of carbon nanofibers (CNFs) with 3D C-IDRA demonstrated enhanced surface area, increased current peak, and superior performance compared to the standalone 3D C-IDRA electrode, as evidenced by a redox amplification factor of 2.94 and a collection efficiency of 81.1%. The results highlight that integrating CNFs with 3D C-IDRA improves the electrochemical performance in detecting DA neurotransmitter. Thus, this discovery elucidates the advantageous potential of the 3D C-IDRA NF electrode in a wide range of applications.

Highly Efficient and Stable Overall Water Splitting Electrocatalyst α-Co(OH)2@PN/NF with Hierarchical and Mesoporous Structure

Exploiting efficient, stable, and cost-effective bifunctional water splitting catalysts is extremely challenging. Here, we developed three-dimensional hierarchical porous catalysts with heterogeneous interfaces, α-Co(OH)2@PN/NF, by a facile two-step electrodeposition approach. This bifunctional electrocatalyst exhibits excellent hydrogen and oxygen evolution performance as well as stability in alkaline aqueous environments. In 1 M KOH solution, small overpotential of 187 mV was needed to drive the hydrogen evolution reaction (HER) at 100 mA cm−2, while the overpotential for the oxygen evolution reaction (OER) was 324 mV at 100 mA cm−2 current density. In addition, the two-electrode electrolytic cell with α-Co(OH)2@PN/NF electrodes for HER and OER required only approximately 1.74 V at 100 mA cm−2 with over 75 h of stable operation. According to the physical-chemical characterization results and electrochemical tests, such excellent performance was attributed to the synergistic effect of the heterogeneous interface and the hierarchical porous structure between α-Co(OH)2 and the nickel oxide layer, as it facilitates the transfer of electrons and the diffusion of ions.

Efficient electrochemical hydrogenation and dehydrogenation of quinoxaline over a dendritic structure P-WO3/NF electrode

Liquid organic hydrogen carrier (LOHC) has been recognized as a highly promising candidate for hydrogen storage materials in addressing hydrogen utilization issues. However, the hydrogenation and dehydrogenation of LOHC typically require noble metal catalysts and harsh reaction conditions. In this paper, we proposed an efficient reversible electrochemical hydrogen storage system based on a nitrogen heterocyclic organic hydrogen carrier, quinoxaline, in which water was used as the solvent and hydrogen source for quinoxaline hydrogenation, and a self-supporting dendritic P-WO3/NF electrode was employed as the electrocatalyst. The catalytic properties of P-WO3/NF for electrochemical hydrogenation of quinoxaline and dehydrogenation of 1,2,3,4-tetrahydroquinoxaline were studied in 1 M KOH solution under mild conditions. The results showed that the hydrogenation conversion of quinoxaline was 90%, the selectivity was 99%, and the dehydrogenation conversion of 1,2,3,4-tetrahydroquinoxaline was 100%, the selectivity was 100%. This indicates that the system has high conversion efficiency, outstanding selectivity, and good reversibility. Meanwhile, the P-WO3/NF electrode adapted to the system exhibited good catalytic stability. In addition, no pre-prepared external hydrogen was required in the electrochemical hydrogenation reaction involving water, which gave the system an excellent safety profile. The reversible electrochemical hydrogen storage system established by this work broadens the vision of LOHC in hydrogen storage applications.

Ru nanoparticles immobilized on self-supporting porphyrinic MOF/nickel foam electrode for efficient overall water splitting

To achieve carbon neutrality, the development of effective and durable electrodes for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is of utmost importance. Herein, the Ru3.4-PMOF/NF electrode was successfully prepared by immobilizing Ru nanoparticles on porphyrinic metal-organic framework/nickel foam (PMOF/NF), effectively driving both the OER and the HER in an alkaline electrolyte. To achieve 10 mA cm−2, the Ru3.4-PMOF/NF electrode only required overpotentials of 19 and 215 mV for HER and OER, respectively. For overall water splitting, an ultra-low cell voltage of 1.468 V was required to drive 10 mA cm−2, surpassing the performance of the integrated Pt/C and RuO2 couple electrode (1.6627 V). The outperformed electrocatalytic activity could be ascribed to the well-dispersed Ru nanoparticles, the self-reconstruction of PMOF, the synergistic effect, and the lamellar morphology. This study offers a promising approach for the development of ruthenium-doped electrodes that can enhance the efficiency of electrocatalytic water splitting.

A CoMo@NiC2O4/NF anode and a Pb/CP cathode for a novel direct sodium borohydride-maleic acid fuel cell

CoMo@NiC2O4/NF and Pb/CP electrodes are prepared, which are used as the anode and cathode, respectively, to assemble a novel direct sodium borohydride-maleic acid fuel cell.

Nickel foam supported biochar doped Ni–Mo bimetallic oxide for supercapacitor application

A novel C-MoO3-NiO2/NF electrode derived from polyoxometalate and rice is obtained and provides a new strategy for the development of high-performance supercapacitors.

Flake-like SnS anchored on the carbon layer for supercapacitor electrode with photo-responsive capacitance enhancement

Photo-responsive supercapacitors incorporate light-responsive materials on capacitive electrodes, making them capable of solar energy conversion and storage within single device. Herein, composite structures consisting of flake-like stannous sulfide (SnS) anchored on a carbon layer (CL) covered nickel foam (CL@SnS/NF) are synthesized as photo-responsive supercapacitor electrode for capacitance enhancement under visible light. SnS as a light-absorbing layer has a narrow bandgap that matches well with the wavelength of visible light, while CL serves as an electron transport channel for effective separation of photogenerated carriers. Due to the synergetic effect of two components above, the areal specific capacitance of the CL@SnS/NF electrode increases from 15.7 to 21.0 mF·cm−2 in light conditions under 0.1 mA·cm−2, which is 1.7 and 6.6 times larger than that of CL/NF and SnS/NF electrodes under the same conditions, respectively, indicating the remarkable light-induced capacitance enhancement performance. The CL@SnS/NF electrode also presents higher photocurrent and photovoltage than two single electrodes, implying its excellent photosensitivity. In addition, the assembled CL@SnS/NF-based symmetric supercapacitor exhibits great capacitance gain under illumination (185.8% at 50 µA·cm−2) and excellent capacitance maintenance (87.7% over 6000 cycles). This work supplies a novel strategy to the development of high-performance solar energy conversion and storage devices.

Integrating 1D/2D nanostructure based on Ni–Co-oxalate for energy storage applications

The performance of an electrochemical energy storage device highly depends on the electrode material. Currently, metal oxalates are evolving as low-cost and stable electrode materials for batteries and supercapacitors. Herein, mixed metal oxalate (NixCo1-xC2O4/NF) based binder-free electrode was fabricated. The nickel foam contributed not only as a substrate but also as a nickel source. The NixCo1-xC2O4/NF confirmed the crystalline phase through X-ray diffraction spectroscopy (XRD). Scanning electron microscopy (SEM) and transmission electron spectroscopy (TEM) confirmed the integrated 1D/2D-like morphology of NixCo1-xC2O4/NF. The electrochemical results reveled the NixCo1-xC2O4/NF electrode exhibit battery behavior with capacity retention of 86.58 % and possessed the highest specific capacity of 470.012 C g−1 at 1 A g-1. Hence, the nickel inclusion during the synthesis has further enhanced the overall properties and performance of the NixCo1-xC2O4/NF electrode.

Interface engineering of heterogeneous NiMn layered double hydroxide/vertically aligned NiCo2S4 nanosheet as highly efficient hybrid electrocatalyst for overall seawater splitting

We report the fabrication of a heterogeneous catalyst through vertically aligned NiCo2S4/Ni3S2 nanosheet with encapsulation of ultrathin NiMn layered double hydroxide over self-standing nickel foam (NM/NCS/NS/NF) via two-step hydrothermal processes. Benefiting from more adequate catalytic active centres and copious interfacial charge transfer channels, NM/NCS/NS/NF electrode demonstrates superior bifunctional activity for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) processes under alkaline fresh/simulated seawater electrolyte conditions. As a result, NM/NCS/NS/NF electrode requires the smallest overpotentials of 282 & 312 mV (OER) and 171 & 204 mV (HER) to attain current densities of 30 & 50 mA cm−2 respectively under alkaline simulated seawater electrolyte conditions. Besides, the presence of amorphous NiMn LDH layers over crystalline NiCo2S4/Ni3S2 catalyst stimulates surface adsorption of oxygen intermediate species, water dissociate ability on catalytic active centres, and mass transport with electron transfer at the interface. Further, the two-electrode configuration assisted electrolyser system delivers an efficient overall water splitting activity with minimum cell voltages of 1.54 V (in 1 M KOH) and 1.56 V (in 1 M KOH+0.5 M NaCl) at a current density of 10 mA cm−2. Besides, a fabricated electrolyser cell provides a more sustained water electrolysis process and robust durability for 20 h which displays NM/NCS/NS/NF electrode is a vibrant and potential candidate for realistic seawater electrolysis. Therefore, our proposed heterogeneous electrocatalyst could open up a new platform for developing efficient large-scale efficient seawater electrolysis.

Hydrogen peroxide electrosynthesis with nickel foam electrodes: influence mechanism of surface oxidation

AbstractBACKGROUNDNickel foam (NF) is widely used as battery electrode matrix and electrochemical process cathode. However, the surface of NF is prone to oxidation, which may affect its ability to reduce oxygen and produce H2O2, but the influence mechanism is still unclear. In this paper, surface oxidation of the NF was regulated by pickling and drying pretreatment, and the surface oxides were characterized by X‐ray photoelectron spectroscopy (XPS) and energy dispersive X‐ray spectrometry (EDS). The NF was used as the substrate, graphite powder as the catalyst, and PTFE as the binder to prepare graphite‐coated NF composite electrodes. The effect of NF surface oxidation on their ability to generate H2O2 was investigated.RESULTSThe results demonstrated that after pickling and drying, the NF surface generated a large amount of NiO, which increased the charge transfer resistance of the NF by 20.3%, and accelerated further reduction decomposition of H2O2. The rotating ring‐disk electrode (RRDE) tests further confirmed that NiO can reduce the two‐electron oxygen reaction selectivity, which was detrimental to H2O2 electrosynthesis. The graphite‐coated NF composite electrode with pristine NF as the substrate can produce 869.1 mg L−1 of H2O2 and maintain relatively good reusability.CONCLUSIONOverall, the surface oxidation of NF is not conducive to H2O2 electrosynthesis, and it is necessary to prevent oxidation during electrode preparation. This study provides a valuable reference for the preparation of NF electrodes and can promote the further study of in situ H2O2 electrosynthesis. © 2023 Society of Chemical Industry (SCI).

Ruthenium Oxide Nanoparticles Immobilized on Ti3C2 MXene Nanosheets for Boosting Seawater Electrolysis.

Seawater electrolysis represents a viable alternative for large-scale synthesis of hydrogen (H2), which is recognized as the most promising clean energy source, without relying on scarce fresh water. However, high energy cost and harmful chlorine chemistry in seawater limited its development. Herein, an effective catalyst based on a ruthenium nanoparticle-Ti3C2 MXene composite loaded on nickel foam (RuO2-Ti3C2/NF) with an open, fine, and homogeneous nanostructure was devised and synthesized by electrodeposition for high performance and stable overall seawater splitting. To drive a current density of 100 mA cm-2, the RuO2-Ti3C2/NF electrode required a small overpotential of 85 and 351 mV for HER and OER in 1 M KOH with only a slight increase in 1 M KOH seawater (156 and 378 mV for, respectively, HER and OER). An assembled RuO2-Ti3C2/NF-based two-electrode cell required an overpotential of only 1.84 V to acquire 100 mA cm-2 in 1 M KOH seawater and maintained its activity for over 25 h. This low cell voltage effectively prevented chlorine electrochemical evolution without anode protection. These promising results open up new avenues for the effective conversion of abundant seawater resources to hydrogen fuel.

Pseudocapacitive electrode performance of zinc oxide decorated reduced graphene oxide/poly(1,8-diaminonaphthalene) composite

Development of Reduced graphene oxide/Zinc oxide/poly(1,8-diaminonaphthalene) (rGO/ZnO/PDAN) composite and its supercapacitor performance has been evaluated. Functional, crystal and morphological structures along with the thermal stability of the polymer-impregnated composite were studied using analyses such as FTIR, powder XRD, Raman, SEM and TGA techniques. The SEM images showcased the random decoration of irregularly shaped ZnO in between the wrinkled rGO sheets and the PDAN. The defective structure of the hybrid composite contributes capacitive features through electron transfer kinetics. The specific capacitance value for the rGO/ZnO/PDAN composite modified NF electrode in 3 M KOH was found to be 239 F/g at the current density of 0.5 A/g. The capacitance retained is 92 % after 5000 cycles at 5 A/g current density. A solid-state symmetrical supercapacitor device based on a novel rGO/ZnO/PDAN composite was successfully developed, which exhibits the specific capacity (40 at 0.6 A/g), energy density (12.66 Wh/kg) and power density (993 W/kg). The synergistic combination of surface-active nitrogen heteroatoms, extended conjugation and ZnO particles decorated over rGO sheets of rGO/ZnO/PDAN ternary hybrid composite displayed significant structural stability and electrochemical pseudocapacitive performances.

Heterogeneous Structures Consisting of Rod-like ZnO Interspersed with Ce2S3 Nanoparticles for Photo-Sensitive Supercapacitors with Enhanced Capacitive Performance.

Photosensitive supercapacitors incorporate light-sensitive materials on capacitive electrodes, enabling solar energy conversion and storage in one device. In this study, heterogeneous structures of rod-shaped ZnO decorated with Ce2S3 nanoparticles on nickel foam (ZnO@Ce2S3/NF) are synthesized using a two-step hydrothermal method as photosensitive supercapacitor electrodes for capacitance enhancement under visible light. The formation of ZnO@Ce2S3 heterogeneous structures is confirmed using various structural characterization techniques. The area-specific capacitance of the ZnO@Ce2S3/NF composite electrode increased from 1738.1 to 1844.0mFcm-2 after illumination under a current density of 5 mAcm-2, which is 2.4 and 2.8 times higher than that of ZnO and Ce2S3 electrodes under similar conditions, respectively, indicating the remarkable light-induced capacitance enhancement performance. The ZnO@Ce2S3/NF electrode also exhibits a higher photocurrent and photovoltage than the two single electrodes, demonstrating its excellent photosensitivity. The improved capacitance performance and photosensitivity under illumination are attributed to the well-constructed energy-level structure, which stimulates the flow of photogenerated electrons from the outer circuit and the involvement of photogenerated holes in the resulting surface-controlled capacitance. In addition, the assembled ZnO@Ce2S3/NF-based hybrid supercapacitor exhibits a great energy density of 145.0 mWhcm-2 under illumination. This study provides a novel strategy for the development of high-performance solar energy conversion/storage devices.

Enhanced electrocatalytic degradation of acid orange 7 by using double perovskite La2CoxNi1-xMnO6/nickel foam as the electro-Fenton cathodes

Adequate generation of hydrogen peroxide and its subsequent activation into reactive oxygen species (ROS) play a crucial role in the catalytic efficiency of heterogeneous electro-Fenton for the degradation of contaminants. Herein, a series of La2NiMnO6 double perovskite with Co doping (La2CoxNi1-xMnO6) were prepared by a facile sol-gel technique and applied as catalysts in heterogeneous electro-Fenton system to removal acid orange 7 (AO7). Nickel foam was chosen as the supporting substrate for the catalyst owing to its excellent physical properties to accelerate the conversion of O2 to H2O2. La2Co0.5Ni0.5MnO6 achieved 90.22 % of AO7 decomposition rate at 120 min via the heterogeneous electro-Fenton system, which was a significant improvement over the catalytic efficiency of both only NF and La2NiMnO6 electrodes. Further studies have shown that the introduction of Co could heighten the efficient redox recycling of Ni2+/Ni3+ and Mn3+/Mn4+ on the electrode surface, synergically facilitating the conversion of H2O2 to OH. Meanwhile, the three redox pairs (Ni2+/Ni3+, Mn3+/Mn4+ and Co2+/Co3+) also stimulated the production of superoxide radicals (O2−), which was also not negligible in enhancing degradation. Finally, the possible pathway and mechanism of the degradation of AO7 were proposed. This work demonstrates that La2CoxNi1-xMnO6/NF has the potential to be a satisfactory electrode for decomposition of organic dyes in aqueous solution.

Controllable preparation of Cu2S@Ni3S2 grown on nickel foam as efficient seawater splitting electrocatalyst

Seawater is one of the richest hydrogen sources around our environment, so it has a lot of advantages to decompose and produce hydrogen. However, considering that chloride ions in seawater have a strong corrosive action on the electrode. Therefore, the design and exploration of highly effective and antiseptic oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) electrocatalysts were studied. It's worth noting that Cu2S@Ni3S2/NF is engaged as a difunctional electrode in this study, which drives a current density of 10 mA cm−2 with requiring overpotentials of only 78 mV and 170 mV, and highlights its significant selectivity of OER and HER. The results show that the increased activity of Cu2S@Ni3S2/NF electrode can be assigned to the synergistic catalysis of (211) and (110) crystal faces, as well as the transfer and the increase of the number of active sites caused by lattice defects. The results of density functional theory show that Cu2S material has optimal free energy of the adsorbed states for H, indicating that the introduction of Cu2S promotes the kinetics of the reaction. The introduction of Ni3S2 material greatly improves the conductivity of Cu2S@Ni3S2/NF electrode. This paper proposes novel insights into the exploration of environmentally friendly and corrosion resistant difunctional catalysts for seawater splitting.

Simultaneously Enhanced Energy Harvesting and Storage Performance Achieved by 3D Mix‐Phase Mose2‐Nise/NF

AbstractAs an energy harvesting device, the newly emerged thermocell has attracted great interest. However, it requires an additional energy storage device to complete a functional recycling system. As the core part of energy harvesting and storage devices, the design of electrodes with both high thermoelectric and electrochemical conversion efficiencies is particularly important. Herein, a high‐performance thermocell and supercapacitor device are constructed by employing the same mix‐phase MoSe2‐NiSe/NF electrode for both energy harvesting and storage. The thermocell exhibits an enhanced Seebeck coefficient of −1.69 mV K−1 and a superior output of 0.58 mW m−2 K−2 for low‐grade heat harvesting. Meanwhile, the supercapacitor device shows a great energy density of 54 Wh kg−1 at a power density of 806 W kg−1 and excellent cycling stability with a 92.8% retention rate after 50 000 cycles. This work offers a universal approach for the rational design of synergistic electrode materials to simultaneously achieve high‐energy harvesting and storage devices and lays a foundation for the recycling system of thermoelectric harvesting, conversion, and storage.

Defect engineering associated with cationic vacancies for promoting electrocatalytic water splitting in iron-doped Ni2P nanosheet arrays

Transition metal phosphides are highly efficient catalysts that do not rely on noble metals, which have shown great potential in replacing noble metal catalysts and contributing to the advancement of the electrocatalytic hydrogen production industry. To further enhance the catalytic performance of transition metal phosphides, researchers have discovered that cationic vacancy defects can be utilized to regulate their electronic structure, thereby improving their catalytic properties. In this research, we present the successful synthesis of a bifunctional Ni2P electrocatalyst (VFe-Ni2P) with cationic vacancy defects through electrodeposition and acid etching techniques. The introduction of cationic vacancies after acid etching is confirmed by electron paramagnetic resonance (EPR) spectroscopy. The VFe-Ni2P electrocatalyst demonstrates excellent catalytic performance in alkaline environments, achieving a current density of 10 mA∙cm−2 at an overpotential of 52 mV for the hydrogen evolution reaction (HER), and the same current density with an overpotential of 154 mV for the oxygen evolution reaction (OER). Additionally, the VFe-Ni2P/NF electrode exhibits remarkable stability over 1000 cyclic voltammetric cycles for both HER and OER. This study presents a novel approach for the synthesis and performance control of highly-efficient transition metal phosphide electrocatalysts, which holds significant importance in the development and design of new energy materials.

Ag-integrated mixed metallic Co-Fe-Ni-Mn hydroxide composite as advanced electrode for high-performance hybrid supercapacitors

Direct growth of redox-active noble metals and rational design of multifunctional electrochemical active materials play crucial roles in developing novel electrode materials for energy storage devices. In this regard, silver (Ag) has attracted great attention in the design of efficient electrodes. Inspired by the house/building process, which means electing the right land, it lays a strong foundation and building essential columns for a complex structure. Herein, we report the construction of multifaceted heterostructure cobalt-iron hydroxide (CFOH) nanowires (NWs)@nickel cobalt manganese hydroxides and/or hydrate (NCMOH) nanosheets (NSs) on the Ag-deposited nickel foam and carbon cloth (i.e., Ag/NF and Ag/CC) substrates. Moreover, the formation and charge storage mechanism of Ag are described, and these contribute to good conductive and redox chemistry features. The switching architectural integrity of metal and redox materials on metallic frames may significantly boost charge storage and rate performance with noticeable drop in resistance. The as-fabricated Ag@CFOH@NCMOH/NF electrode delivered superior areal capacity value of 2081.9 µA h cm−2 at 5 mA cm−2. Moreover, as-assembled hybrid cell based on NF (HC/NF) device exhibited remarkable areal capacity value of 1.82 mA h cm−2 at 5 mA cm−2 with excellent rate capability of 74.77% even at 70 mA cm−2 Furthermore, HC/NF device achieved maximum energy and power densities of 1.39 mW h cm−2 and 42.35 mW cm−2, respectively. To verify practical applicability, both devices were also tested to serve as a self-charging station for various portable electronic devices.

Construction of binder-free 3-D porous NiMn LDH electrode materials for high performance asymmetric supercapacitors using dynamic hydrogen bubbles as template

Three-dimensional porous Ni/NiMn layered double hydroxides (3-D Ni/NiMn LDH) with enhanced specific capacitance and superior cycle stability were loaded on nickel foam (NNM/NF) by combining dynamic hydrogen bubble template (DHBT) and electrodeposition methods. The optimized NNM-2/NF electrode for supercapacitors (SCs) possessed high specific capacitance (2755.36 F g–1 at 1 A g–1) and considerable capacitance retention (71.25% after 5000 consecutive cycles at 20 A g–1). When NNM-2/NF and active carbon (AC) were used to construct an asymmetric supercapacitor (ASC) device, it achieves a high specific energy density of 41.75 Wh kg–1 at a power density of 2700.09 W kg–1 and an excellent cycling performance (109.85% capacitance retention after 5000 cycles at 20 A g–1). The practical energy storage applicability of this device was demonstrated by the lighting of an LED bulb when two NNM-2/NF//AC devices were connected in series. This work provided potential strategy to promote the further application of porous Ni/NiMn LDH electrodes in new-generation energy storage.

Amorphous MoS2 Decorated Ni3 S2 with a Core-shell Structure of Urchin-Like on Nickel-Foam Efficient Hydrogen Evolution in Acidic and Alkaline Media.

The large-scale commercialization of the hydrogen evolution reaction (HER) necessitates the development of cost-effective and highly efficient electrocatalysts. Although transition metal sulfides, such as MoS2 and Ni3 S2 , hold great potential in the field of HER, their catalytic performance has been unsatisfactory due to incomplete exposure of active sites and poor electrical conductivity. In this work, via a simple hydrothermal strategy, amorphous MoS2 nanoshells in the form of urchin-like MoS2 -Ni3 S2 core-shell heterogeneous structure is realized and in situ loaded on nickel foam (A-MoS2 -Ni3 S2 -NF). In particular, XPS analysis results show that the coupling of amorphous MoS2 and Ni3 S2 makes the electrode surface exhibit electron-abundant property, which will have a positive impact on HER catalytic activity. In addition, the fully exposed active site of amorphous MoS2 is another crucial factor contributing to its high catalytic performance of A-MoS2 -Ni3 S2 -NF electrode. In particular, at a current density of 10mA cm⁻2 , the overpotential of electrode is 95mV (1.0m KOH) and 145mV (0.5m H2 SO4 ). This work highlights the importance of amorphous MoS2 and MoS2 -Ni3 S2 of sea-urchin core-shell structure in optimizing HER performance, which provides an important reference for HER research.